Swine flu strain resistant to Tamiflu is spreading more easily
The flu season is still young in the U.S. and the rest of the Northern Hemisphere, but Australia wrapped up its flu season months ago, and public health officials there have some disturbing news to report: The version of so-called swine flu that is resistant to the drug Tamiflu is spreading more easily in the land Down Under.
For those in need of a refresher course, swine flu refers to the H1N1 flu virus that caused a pandemic in 2009. It emerged in April in Mexico and spread swiftly around the globe, traveling to 214 countries and territories and killing more than 18,000 people, according to the World Health Organization. Humans were unusually vulnerable to this particular strain – a combination of viruses from birds, pigs and people – because their immune systems had never encountered it before.
Tamiflu, also known by the generic name oseltamivir, was frequently prescribed to patients, and it didn’t take long for a version of H1N1 to emerge that was resistant to the drug. Luckily, this strain was a minor player, infecting less than 1% of people who were tested. In those cases, it spread between people only when they were in closed settings or had close contact with one another.
Fast-forward to 2011. In and around the Australian city of Newcastle, the Tamiflu-resistant H1N1 virus was spreading more easily among humans, according to a report being published in Thursday’s edition of the New England Journal of Medicine.
Public health officials took virus samples from 182 patients treated in doctors’ offices and hospitals between May and August. They found that 29 of those samples – or 16% – turned out to be resistant to Tamiflu.
The 29 patients ranged in age from 4 months to 62 years, with a median age of 31; 17 of the patients were female, including three who were pregnant. Among all 29 patients, the most common flu symptoms were cough (experienced by 86% of patients) and fever (affecting 76% of patients). Seven patients required admission to the hospital, but none was treated in the ICU and none died.
Genetic analysis of the flu samples revealed that all of the 29 patients were infected with a single strain. Most of these patients lived within about 30 miles of Newcastle, the seventh largest city in Australia. (Two related strains were detected elsewhere in Australia, including 100 miles away in Sydney, the country’s largest city.)
It’s unclear how the Tamiflu-resistant strain spread from person to person. Eight of the patients lived with another person who was infected, and two other patients rode together in a car. The rest of the patients “had no known epidemiologic link,” according to the report.
The authors of the report, including three scientists working for the World Health Organization, warned flu experts in the Northern Hemisphere to be on the lookout for this flu strain – or any other strain that is resistant to Tamiflu – this winter.
A link to the report is available here.
Return to the Booster Shots blog.